One of the variables which limit the increase of efficiency and capacity in the compressors is overheating. The limitation comes from the thermal exchange between the gas being drawn through the evaporation line and the interior of the compressor, causing the increase in the refrigerant temperature before compression. This situation results in loss of capacity and, consequently, in loss of efficiency. The discharge system, usually presenting a high temperature, contributes to increase the thermal profile of the compressor. Therefore, insulating the discharge heat results in reducing the thermal profile as a whole and, most importantly, of the temperature in which the gas is compressed. Usually, the strategy to prevent the gas from overheating is to improve the suction insulation.
However, there are known solutions aiming the thermal insulation of the discharge in refrigeration compressors. Among said solutions, US2010/0226805 (ACC) discloses a discharge line in which is provided a discharge tube in plastic material, and a tubular sleeve, in plastic or polymer, for example, PTFE, which is located surrounding a portion of the discharge tube, in the region the latter passes through the discharge tube located in the compressor housing, such tube being metallic in this prior solution. Although this solution presents a small reduction in the heat transmission to the interior of the compressor, it has the drawback of preventing only the transmission of heat of the discharge gas, in the discharge tube, to the interior of the environment of the hermetic housing, considering that said discharge tube is usually metallic and of large extension, in order to absorb the vibrations between the compressor assembly and the hermetic housing. This prior solution does not prevent the discharge gas heat, which is released to the discharge chamber inside the cylinder cap, from being transferred to the head region of the compressor and to the remaining of the metallic parts of the assembly, particularly to the cylinder crankcase, contributing to the undesired heating of the gas to be compressed.
Another known solution (DE102004054328—Denso) provides a discharge chamber internally provided with a thermal insulating means in the form of an inner lining directly seated against the inner wall of the discharge chamber. This prior solution has the drawback of allowing for a certain thermal exchange, through conduction, between the gas contained inside the discharge chamber and the cylinder cap, considering that the proposed thermal insulation takes the form of a lining applied internally to the cylinder cap, without any spacing between said thermal insulation and the metallic material of the cylinder cap. This technical solution is not able to provide an effective thermal insulation between the gas being released to the interior of the discharge chamber and the assembly formed by the metallic structure of the cylinder cap, valve plate and cylinder crankcase.